Forget what your dentist told you: There's little good evidence you should floss

It's a key part of your oral hygiene routine, right alongside brushing. It's almost universally recommended by dentists. It makes intuitive sense, directly tackling the narrow canyons between your teeth.

But there isn't a lot of evidence that it works.

Associated Press reporter Jeff Donn fact-checked the American Dental Association's (ADA's) claim, which the US government has backed since 1979, that "flossing is an essential part of taking care of your teeth and gums." Donn found that, out of 25 recent studies comparing a toothbrush alone to brushing and flossing, none produced reliable evidence of a benefit. Rather, reviews found the evidence for flossing weak to nonexistent, and researchers suggested that any minor benefits might be so minimal that most people wouldn't feel the difference.

Still, major dental associations back up the idea that people should floss. As Donn reports, the ADA and American Academy of Periodentology (AAP) pointed toward studies that suggest flossing reduces plaque and improves overall oral health. But most of those studies were too limited to be reliable or conclusive. When pressed, AAP President Wayne Aldredge told Donn that he believes flossing reduces gum disease.

"It's like building a house and not painting two sides of it," he told Donn. "Ultimately those two sides are going to rot away quicker."

Donn also found that major floss makers, which fund most research into floss, couldn't provide reliable evidence that flossing improves oral health. When pressed on the matter, they declined to comment.

When the AP filed Freedom of Information Act requests in 2015 for the US federal government's evidence in favor of flossing, the recommendation that people floss did not show up in the next round of dietary guidelines. According to Donn's report, in a letter to the AP, the government said the claim had never been researched as required.

When the Cochrane Collaboration, a respected panel of independent experts, reviewed the evidence in favor of flossing, their findings largely echoed Donn's. They said that while there was "some evidence" that flossing helped reduce gingivitis, there was only "weak, unreliable evidence" of an association with plaque reduction. The panel also found that there were "no studies" that showed flossing helped prevent cavities.

Donn found some prominent dentists who went on the record saying the benefits of flossing are overstated, but most maintained that people should still floss:

National Institutes of Health dentist Tim Iafolla acknowledged that if the highest standards of science were applied in keeping with the flossing reviews of the past decade, "then it would be appropriate to drop the floss guidelines."

Regardless, he added, Americans should still floss.

"It's low risk, low cost," he said. "We know there's a possibility that it works, so we feel comfortable telling people to go ahead and do it."

Expect a lot more research on the subject to come out in the near future. In the meantime, it's still probably a good idea to follow your dentist's recommendations.